Optical pickup apparatus and optical disk drive apparatus

ABSTRACT

An optical pickup apparatus for reproducing information from an optical disk, includes: a semiconductor laser applying a beam to an optical disk having two recording layers through an objective lens; and a light receiving device to which light reflected from the optical disk is directed through the objective lens and a beam splitting device, wherein: the beam splitting device has two first light receiving areas for detecting a push-pull signal and a second light receiving area for detecting a focus error signal, and a configuration is provided such that the center of the optical axis of the reflected light in the beam splitting device is made to lie within the second light receiving area for detecting the focus error signal.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an optical pickup apparatus and anoptical disk drive apparatus such as an optical card apparatus or so.

2. Description of the Related Art

FIG. 1 shows a general configuration of an optical pickup apparatusprovided in an optical disk drive apparatus. As shown, the opticalpickup apparatus handles an optical disk 8 and includes a semiconductorlaser 1, a glass plate 2, a grating 3 formed on a side of the glassplate, which side faces the semiconductor laser 1, for generating threebeams, a hologram 4 formed on a side of the glass plate, which side isopposite to the side on which the grating 3 is formed, a hologram pickup5, a collimator lens 6, an objective lens 7, and a light receivingdevice 9.

FIG. 2 shows an internal side view of the hologram pickup 5. As shown,the hologram pickup 5 includes the semiconductor laser 1 and the lightreceiving device 9 mounted on a substrate, and also, the glass plate 2,grating 3 and hologram 4 arranged to face the semiconductor laser 1, andthus, these parts/devices form a unit.

A beam emitted from the semiconductor laser 1 is split into a main beam(0-th light) and two sub-beams (±1-st lights) by means of the grating 3functioning as a diffraction grating for the three beams, and afterthat, reaches the hologram 4. Then, only a light (0-th light)transmitted by the hologram 4 is made to become a parallel beam by meansof the collimator lens 6, and is collected onto the optical disk 8 afterpassing through the objective lens 7. Returning lights of the main beamand sub-beams reflected by the optical disk 8 are directed to thehologram 4 after again passing through the objective lens 7 andcollimator lens 6. Then, at this time, only a light (1-st diffractedlight) diffracted by the hologram 4 is applied to the light receivingdevice 9, and is used for generating various signals which will bedescribed later.

The optical disk 8 includes two recording layers 8 a and 8 b with aseparation of tens of μm (on the order of a range between 40 and 70 μm),and FIG. 1 shows a case where the beam applied is made to focus in therecording layer 8 a nearer to the objective lens 7. Reflected light 10indicated by a solid line in FIG. 1 is a beam which has been reflectedby the recording layer 8 a nearer to the objective lens 7, whilereflected light 11 indicated by a broken line is a beam which wasreflected by the recording layer 8 b farther from the objective lens 7.

FIG. 3 illustrates a state of the reflected light 10 from the recordinglayer 8 a and the reflected light 11 from the recording layer 8 b in thehologram 4. As shown, the hologram 4 is separated into three areas AB, Cand D defined by two separating lines.

FIG. 4 illustrates a state of the reflected light 10 from the recordinglayer 8 a and the reflected light 11 from the recording layer 8 b on thelight receiving device 9. The total three beams, i.e., the main beam andtwo sub-beams provided by the grating 3 are split by the hologram 4. Asa result, the reflected light 10 from the recording layer 8 a forms ninespots while the reflected light 11 from the recording layer 8 b formsnine flare without focusing.

As shown in FIG. 4, the light receiving device 9 includes eight lightreceiving surfaces ‘a’ through ‘h’, and relationship between beamsobtained from the diffraction by the above-mentioned three areas AB, Cand D of the hologram 4 and the light receiving surfaces receiving thesebeams respectively is as follows:

the diffracted light of the main beam from the area AB is receivedbetween the light receiving surfaces ‘a’ and ‘b’;

the diffracted lights of the sub-beams from the area AB are receivedoutside of the light receiving surfaces ‘a’ and ‘b’, respectively (inother words, these are not substantially received by any of the lightreceiving surfaces);

the diffracted light of the main beam from the area C is received by thelight receiving surface ‘c’;

the diffracted lights of the sub-beams from the area C are received bythe light receiving surfaces ‘e’ and ‘g’, respectively;

the diffracted light of the main beam from the area D is received by thelight receiving surface ‘d’; and

the diffracted light of the sub-beams from the area D are received bythe light receiving surfaces ‘f’ and ‘h’ respectively.

By expressing the various signals obtained from the respective lightreceiving surfaces ‘a’ through ‘h’ by the respective same symbols ‘a’through ‘h’, a focus error signal FES is expressed by:

FES=a−b.

A tracking error signal TES is expressed by:

TES=(c−d)−α((e+g)−(f+h)).

A tracking cross signal TCS is expressed by:

TCS=(c+d)−α((e+g)+(f+h)).

A lens position signal LPS is expressed by:

LPS=(c−d)+α((e+g)−(f+h))

An information reproducing signal RFS is expressed by:

RFS=a+b+c+d.

These relationships are obtained according to a so-called differentialpush-pull method well known.

Japanese patent No. 2594445 (registered in Dec. 19, 1996 and entitled‘Hologram Optical Head’, the inventors: Shuichi Onayama et al.) andJapanese laid-open patent application No. H11-353698 (published in Dec.24, 1999, entitled ‘Optical Pickup Apparatus’, the inventor: MasahikoNakayama) disclose the background arts. Specifically, Japanese patentNo. 2594445 discloses a hologram for a hologram optical head having acircular area at the center for making easier spot adjustment forreturning light (see FIG. 1 of this patent). Japanese laid-open patentapplication No. H11-353698 discloses an optical pickup apparatusdiffracting reflected light from an optical disk by means of a hologramso as to direct it toward a light receiving device (see FIG. 1 of thislaid-open patent application)

FIG. 5 shows a general configuration of another optical pickup apparatusin an optical disk drive apparatus. As shown, the optical pickupapparatus handles an optical disk 108 and includes a semiconductor laser101, a glass plate 102, a grating 103 formed on a side of the glassplate, which side faces the semiconductor laser 101, for generatingthree beams, a hologram 104 formed on a side of the glass plate, whichside is opposite to the side on which the grating 103 is formed, ahologram pickup 105, a collimator lens 106, an objective lens 107, and alight receiving device 109.

FIG. 6 shows an internal side view of the hologram pickup 105. As shown,the hologram pickup 105 includes the semiconductor laser 101 and thelight receiving device 109 mounted on a substrate, and also, the glassplate 102, grating 103 and hologram 104 arranged to face thesemiconductor laser 101, and thus, these parts/devices form a unit.

A beam emitted from the semiconductor laser 101 is split into a mainbeam (0-th light) and two sub-beams (±1-st lights) by means of thegrating 103 functioning as a diffraction grating for the three beams,and after that, reaches the hologram 104. Then, only a light (0-thlight) transmitted by the hologram 104 is made to become a parallel beamby means of the collimator lens 106, and is collected onto the opticaldisk 108 after passing through the objective lens 107. Returning lightsof the main beam and sub-beams reflected by the optical disk 108 aredirected to the hologram 104 after again passing through the objectivelens 107 and collimator lens 106. Then, at this time, only a light (1-stdiffracted light) diffracted by the hologram 104 is applied to the lightreceiving device 109, and is used for generating various signals.

FIG. 7 illustrates a state of the reflected light 110 from the opticaldisk 108, on the hologram 104. As shown, the hologram 104 is separatedinto three areas AB, C and D by two separating lines. In FIG. 7, zoneshatched denote zones at which a push-pull component occurs. Details ofthe push-pull signal are disclosed by Japanese patent publication No.H04-3013 (published on Jan. 21, 1992, entitled ‘Optical Track PositionDetection Apparatus and Optical Recording/reproduction Apparatusapplying it’, inventors: Shigeru Nakamura et al.)

Specifically, Japanese patent publication No. H04-3013 discloses anoptical detector for detecting tracking error provided in a formsymmetrical with respect to the track direction and disposed in a regionwithin an interference region of 0-th diffracted light and ±1 diffractedlight and further narrowed for the amount of maximum moving range ofoptical axis error of the reflected light caused in a tracking processor by disk inclination (see FIG. 9 of this publication).

FIG. 8 illustrates a state of the reflected light 110 from the opticaldisk 108, on the light receiving device 109. As shown, the lightreceiving device 109 includes eight light receiving surfaces ‘a’ through‘h’, and relationship between beams obtained from the diffraction by theabove-mentioned three areas AB, C and D of the hologram 4 and the lightreceiving surfaces receiving these beams respectively is as follows:

the diffracted light of the main beam from the area AB is receivedbetween the light receiving surfaces ‘a’ and ‘b’;

the diffracted lights of the sub-beams from the area AB are receivedoutside of the light receiving surfaces ‘a’ and ‘b’, respectively (inother words, are not substantially received by any light receivingsurfaces);

the diffracted light of the main beam from the area C is received by thelight receiving surface ‘c’;

the diffracted lights of the sub-beams from the area C are received bythe light receiving surfaces ‘e’ and ‘g’, respectively;

the diffracted light of the main beam from the area D is received by thelight receiving surface ‘d’; and

the diffracted lights of the sub-beams from the area D are received bythe light receiving surfaces ‘f’ and ‘h’ respectively.

By expressing the various signals obtained from the respective lightreceiving surfaces ‘a’ through ‘h’ by the same symbols ‘a’ through ‘h’respectively, a focus error signal FES is expressed by:

FES=a−b.

A tracking error signal TES is expressed by:

TES=(c−d)−α((e+g)−(f+h)).

A tracking cross signal TCS is expressed by:

TCS=(c+d)−α((e+g)+(f+h))

A lens position signal LPS is expressed by:

LPS=(c−d)+α((e+g)−(f+h))

An information reproducing signal RFS is expressed by:

RFS=a+b+c+d.

In the push-pull signal (PPS) obtained from the hatched zones shown inFIG. 7, the rate at which this signal is included in the areas C and Dis 50% of the whole signal amount as shown. This signal amount issufficient in case where information such as addresses or so is detectedfrom a pre-groove of a CD-R/RW.

Other than the above-mentioned Japanese laid-open patent publication No.H04-3013, Japanese laid-open patent application No. H11-353698(mentioned above) also discloses the background art.

SUMMARY OF THE INVENTION

In FIG. 4, on the respective light receiving surfaces of the lightreceiving device 9, not only the reflected lights from the recordinglayer 8 a, but also reflected lights from the recording layer 8 b areapplied unevenly. Thereby, the above-mentioned signals FES, TES, TCS,LPS and RFS may not be detected properly.

In order to solve this problem, the present invention has an object toprovide an optical pickup apparatus and an optical disk apparatus bywhich, especially in case where the beam focuses in the recording layernearer to the objective lens, an adverse influence applied to thevarious signals caused by the reflected light 11 coming from therecording layer farther from the objective lens, in other words, theflares, can be effectively reduced, and thus, the various signals can beobtained properly.

An optical pickup apparatus according to the present invention forreproducing information from an optical disk includes: a semiconductorlaser applying a beam to an optical disk having two recording layersthrough an objective lens; and a light receiving device to which lightreflected from the optical disk is directed through the objective lensand a beam splitting device, wherein: the beam splitting device has twofirst light receiving areas for detecting a push-pull signal and asecond light receiving area for detecting a focus error signal, and aconfiguration is provided such that the center of the optical axis ofthe reflected light in the beam splitting device is made to lie withinthe second light receiving area for detecting the focus error signal.

Thereby, it is possible to effectively reduce the adverse influenceexerted upon various signal such as a focus error signal (FES), atracking error signal (TES), a tracking cross signal (TCS), a lensposition signal (LPS) and an information reproducing signal (RFS),caused by the reflected light, i.e., flare from the recording layerfarther from the objective lens when focus occurs in the recording layernearer to the objective lens.

It is preferable in the above-mentioned configuration of the opticalpickup apparatus that lines defining the three light receiving areascomprise three straight lines and a curved line. Thereby, it is possibleto increase the signal amounts of the components of the tracking errorsignal (TES) and tracking cross signal (TCS) and also, to improve thesignal quality in the tracking error signal (TES), tracking cross signal(TCS) and lens position signal (LPS).

It is preferable in the above-mentioned configuration of the opticalpickup apparatus that lines defining the three light receiving areascomprise three straight lines, and each of at least two angles formedbetween respective ones of these lines is more than 90 degrees. Thereby,it is possible to increase the signal amounts of the components of thetracking error signal (TES) and tracking cross signal (TCS) and also, toimprove the signal quality in the tracking error signal (TES), trackingcross signal (TCS) and lens position signal (LPS).

It is preferable in any of the above-mentioned configurations of theoptical pickup apparatus that, when the beam from the objective lens ismade to focus in the recording layer nearer to the objective lens fromamong the two recording layers of the optical disk, the reflected lightfrom the recording layer farther from the objective lens from among thetwo recording layers is applied to the second light receiving area fordetecting the focus error signal.

Thereby, it is possible to completely eliminate the adverse influenceexerted upon the various signal such as the focus error signal (FES),tracking error signal (TES), tracking cross signal (TCS), lens positionsignal (LPS), information reproducing signal (RFS), caused by thereflected light, i.e., flare from the recording layer farther from theobjective lens when focus occurs in the recording layer nearer to theobjective lens.

According to another aspect of the present invention, an optical pickupapparatus for reproducing information from an optical disk includes: asemiconductor laser applying a beam to an optical disk having tworecording layers through an objective lens; and a light receiving deviceto which light reflected from the optical disk is directed through theobjective lens and a beam splitting device, wherein: the beam splittingdevice has two first light receiving areas for detecting a push-pullsignal, a second light receiving area for detecting a focus error signaland a fourth light receiving area including the optical axis of thereflected light.

Thereby, it is possible to completely eliminate the adverse influenceexerted upon the various signal such as the focus error signal (FES),tracking error signal (TES), tracking cross signal (TCS), lens positionsignal (LPS), information reproducing signal (RFS), caused by thereflected light, i.e., flare from the recording layer farther from theobjective lens when focus occurs in the recording layer nearer to theobjective lens.

It is preferable in the above-mentioned configurations of the opticalpickup apparatus that the beam splitting device comprises a hologramdevice. Thereby, it is possible to provide an inexpensive optical pickupapparatus.

It is preferable to employ any of the above-mentioned configurations ofthe optical pickup apparatus in an optical disk drive apparatus.Thereby, it is possible to provide an optical disk drive apparatushaving an improved reliability in particular in terms of signalreproduction performance.

Recently, a DVD+RV/+R has spread widely which is a recording mediumderived from the above-mentioned CD-R/RW but has a larger storagecapacity. A pre-groove in the DVD+RW/+R wobbles as being modulated athigher speed than that in the CD-R/RW, and, as in the case of CD-R/RW,information such as addresses or so is read out from the pre-groove witha use of the above-mentioned push-pull signal. While the groove pitch is1.6 μm in the CD-R/RW, the groove pitch is as small as 0.74 μm in theDVD+RW/+R. As a result, the amount of the push-pull signal obtainedtherefrom is very small in the case of DVD+RW/+R. As the modulation ismade at high speed as mentioned above and also the signal amount itselfis small as mentioned above, it is difficult to properly read out theinformation such as addresses or so from the pre-groove in case of theDVD+RW/+R with the same method as that provided for CD-R/RW.

Accordingly, another object of the present invention is to solve thisproblem, and to provide an optical pickup apparatus and an optical diskdrive apparatus by which, especially, the information such as addressesor so written in the pre-grove of the DVD+RW/+R can be properlydetected.

According to another aspect of the present invention, an optical pickupapparatus for reproducing information from an optical disk includes: asemiconductor laser applying a beam to an optical disk having tworecording layers through an objective lens; and a light receiving deviceto which light reflected from the optical disk is directed through theobjective lens and a beam splitting device, wherein: the beam splittingdevice has two first light receiving areas for detecting a push-pullsignal and a second light receiving area for detecting a focus errorsignal, and the amount of the push-pull signal detected in the two firstlight receiving areas for detecting the push-pull signal is more than50% of the total amount of the push-pull signal obtained from theoptical disk. Thereby, it is possible to properly detect the informationsuch as addresses or so written in the pre-groove of the DVD+RW/+R.

It is preferable in the above-mentioned configuration of the opticalpickup apparatus that lines defining the three light receiving areascomprise three straight lines and a curved line. Thereby, it is possibleto utilize a conventionally used circuit for signal detection fordetecting the information such as addressees written in the pre-grooveof the DVD+RW/+R, for example.

It is preferable in the above-mentioned configuration of the opticalpickup apparatus that lines defining the three light receiving areascomprise three straight lines, and each of at least two angles formedbetween respective ones of these lines is more than 90 degrees. Thereby,it is possible to simplify the configuration of the beam splittingdevice, and thus, it is possible to employ an optical part such as aprism or so for example other than a hologram as the beam splittingdevice.

It is preferable in any of the above-mentioned configurations of theoptical pickup apparatus that the beam splitting device is a hologramdevice. Thereby, it is possible to provide an inexpensive optical pickupapparatus.

It is preferable to employ any of the above-mentioned configurations ofthe optical pickup apparatus in an optical disk drive apparatus.Thereby, it is possible to provide an optical disk drive apparatushaving an improved reliability in particular in terms of signalreproduction performance.

BRIEF DESCRIPTION OF THE DRAWINGS

Other objects and further features of the present invention will becomemore apparent from the following detailed description when read inconjunction with the following accompanying drawings:

FIG. 1 illustrates a general configuration of an optical system of anoptical pickup apparatus of an optical disk drive apparatus;

FIG. 2 shows an internal side view of a hologram pickup shown in FIG. 1;

FIG. 3 illustrates a state of reflected light from a recording layer ofan optical disk nearer to an objective lens and reflected light from arecording layer farther from the objective lens in a hologram shown inFIG. 2;

FIG. 4 illustrates a state of the reflected light diffracted by thehologram shown in FIG. 4 in a light receiving device shown in FIG. 2;

FIG. 5 illustrates another general configuration of an optical system ofan optical pickup apparatus of an optical disk drive apparatus;

FIG. 6 shows an internal side view of a hologram pickup shown in FIG. 5;

FIG. 7 illustrates a state of reflected light from a recording layernearer to an objective lens and reflected light from a recording layerfarther from the objective lens in a hologram shown in FIG. 6;

FIG. 8 illustrates a state of the reflected light diffracted by thehologram shown in FIG. 7 in a light receiving device shown in FIG. 6;

FIG. 9 shows a configuration of a hologram provided in an optical pickupapparatus according to a first embodiment of the present invention;

FIG. 10 shows a state of reflected light from a recording layer of anoptical disk nearer to an objective lens and reflected light from arecording layer of the optical disk farther from the objective lensafter being diffracted by the hologram shown in FIG. 9 in the lightreceiving device shown in FIG. 2;

FIG. 11 shows a configuration of a hologram provided in an opticalpickup apparatus according to a second embodiment of the presentinvention;

FIG. 12 shows a configuration of a hologram provided in an opticalpickup apparatus according to a third embodiment of the presentinvention;

FIG. 13 shows a configuration of a hologram provided in an opticalpickup apparatus according to a fourth embodiment of the presentinvention;

FIG. 14 shows a configuration of a hologram provided in an opticalpickup apparatus according to a fifth embodiment of the presentinvention;

FIGS. 15A and 15B illustrate a state of the reflected light diffractedby the hologram shown in FIG. 14 in a light receiving device accordingto the fifth embodiment;

FIG. 16 shows a general functional block diagram of an optical diskdrive apparatus according to an embodiment of the present invention;

FIG. 17 shows a general block diagram of an information processingapparatus employing the optical disk drive apparatus shown in FIG. 16;

FIG. 18 shows a configuration of a hologram provided in an opticalpickup apparatus according to a sixth embodiment of the presentinvention;

FIG. 19 shows a configuration of a hologram provided in an opticalpickup apparatus according to a seventh embodiment of the presentinvention;

FIG. 20 shows a configuration of a hologram provided in an opticalpickup apparatus according to an eighth embodiment of the presentinvention;

FIG. 21 shows a configuration of a hologram provided in an opticalpickup apparatus according to a ninth embodiment of the presentinvention;

FIG. 22 shows a general functional block diagram of an optical diskdrive apparatus according to another embodiment of the presentinvention; and

FIG. 23 shows a general block diagram of an information processingapparatus employing the optical disk drive apparatus shown in FIG. 22.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Embodiments of the present invention will now be described withreference to figures.

Each of first through fourth embodiments of the present invention whichwill now be described has a configuration same as the optical pickupapparatus described above with reference to FIGS. 1 through 4 except thehologram 4, and a fifth embodiment of the present invention has aconfiguration same as the optical pickup apparatus described above withreference to FIGS. 1 through 4 except the hologram 4 and the lightreceiving device 9, as will be described.

FIG. 9 illustrates a hologram 20 provided in an optical pickup apparatusin a first embodiment of the present invention, which hologram acts as abeam splitting device.

In the first embodiment, instead of the hologram 4 provided in theabove-described optical pickup apparatus shown in FIG. 1, the hologram20 is formed on the glass plate 2.

The hologram 20 includes total three areas, i.e., two areas C and D fordetecting a push-pull signal and an area AB for detecting a focus errorsignal, and these areas are formed by separating lines, i.e., threestraight lines L1, L2 and L3, and a curved line L4 Specifically, withrespect to the center of the above-mentioned reflected light 10 comingfrom the above-mentioned recording layer 8 a, the approximatelysemicircular line L4 and the two lines L2 and L3 extending from bothends P2 and P3 of the curved line L4 divides the hologram 20 into twoareas. One of the thus-obtained two areas including the center of thereflected light 10 is the above-mentioned area AB. The remaining area isfurther divided into the two areas by the straight line L1 into twoareas which are the above-mentioned areas C and D.

The radius of the above-mentioned approximately semicircular curved lineL4 should be determined to be larger than the radius of the spot formedby the above-mentioned reflected light 11 from the above-mentionedrecording layer 8 b on the hologram 20 when the reflected light 11 isapplied to the hologram 20. As a result, as the diameter of the spotformed by the reflected light 10 from the recording layer 8 a nearer tothe objective lens 7 when the reflected light 10 is applied to thehologram 20 is larger than the diameter of the spot formed by thereflected light 11 from the recording layer 8 b when the reflected light11 is applied to the hologram 20, the reflected light 10 from therecording layer 8 a is applied to the areas AB and areas C and D whilethe reflected light 11 from the recording layer 8 b is applied to thearea AB, as shown in FIG. 9.

FIG. 10 illustrates a state of the reflected light from the recordinglayer nearer to the objective lens and the reflected light from therecording layer farther from the objective lens after being diffractedby the hologram 20 described above. As the reflected light from therecording layer 8 b is applied to the area AB as mentioned above, flaresof the reflected light 11 from the recording layer 8 b is applied onlyto the above-mentioned light receiving surfaces ‘a’ and ‘b’ uniformly.As a result, the focus error signal expressed by:

FES=a−b,

the tracking error signal expressed by:

TES=(c−d)−((e+g)−(f+h)),

the tracking cross signal expressed by:

TCS=(c+d)−α((e+g)+(f+h)),

the lens position signal expressed by:

LPS=(c−d)+α((e+g)−(f+h)), and

the information reproducing signal expressed by:

RFS=a+b+c+d

can be properly detected respectively.

FIG. 11 illustrates a hologram 21 provided in an optical pickupapparatus in a second embodiment of the present invention, whichhologram also acts as a beam splitting device.

In the second embodiment, instead of the hologram 4 provided in theabove-described optical pickup apparatus shown in FIG. 1, the hologram21 is formed on the glass plate 2. This hologram 21 is such that thepositions of the straight lines L2 and L3 which divides the holograminto the area AB and areas C and D in the hologram 20 described abovewith reference to FIG. 9 are shifted in a direction indicated by anarrow A1 shown in FIG. 11, i.e., in the direction opposite to the sideof the separating line L1 which defines the areas C and D with respectto the center of the reflected light 10 from the recording layer 8 a.Thereby, the areas by which the push-pull signal is detected areincreased.

By configuring the hologram 21 as described above, as in theabove-described first embodiment, the adverse influence caused by theflares of the reflected light 11 from the recording layer 8 b can bereduced effectively, and also, the qualities of the tracking errorsignal expressed by:

TES=(c−d)−α((e+g)−(f+h)),

the tracking cross signal expressed by:

TCS=(c+d)−α((e+g)+(f+h)), and

the lens position signal expressed by:

LPS=(c−d)+α((e+g)−(f+h))

are improved.

FIG. 12 illustrates a hologram 22 provided in an optical pickupapparatus in a third embodiment of the present invention, which hologramalso acts as a beam splitting device.

In the third embodiment, instead of the hologram 4 provided in theabove-described optical pickup apparatus shown in FIG. 1, the hologram22 is formed on the glass plate 2. This hologram 22 is such that thepositions of the straight lines L2 and L3 which divides the holograminto the area AB and areas C and D in the hologram 20 described abovewith reference to FIG. 9 are rotated in respective directions indicatedby arrows A2 and A3 shown in FIG. 12 about the points P2 and P3 at whichthe curved line L4 and the straight lines L2 and L3 are connected shownin FIG. 9, respectively. Thereby, the areas by which the push-pullsignal is detected are increased.

By configuring the hologram 22 as described above, as in theabove-described first embodiment, the adverse influence caused by theflares of the reflected light 11 from the recording layer 8 b can bereduced effectively, and also, the qualities of the tracking errorsignal expressed by:

TES=(c−d)−α((e+g)−(f+h)),

the tracking cross signal expressed by:

TCS=(c+d)−α((e+g)+(f+h)), and

the lens position signal expressed by:

LPS=(c−d)+α((e+g)−(f+h))

are improved.

FIG. 13 illustrates a hologram 23 provided in an optical pickupapparatus in a fourth embodiment of the present invention, whichhologram also acts as a beam splitting device.

In the fourth embodiment, instead of the hologram 4 provided in theabove-described optical pickup apparatus shown in FIG. 1, the hologram23 is formed on the glass plate 2.

In order to divide the hologram 23 into three areas, three separatinglines L11, L12 and L13 each of which is a straight line are used asshown in FIG. 13, where each of at least two angles θ1 and θ2 formedbetween respective ones of these separating lines L11, L12 and L13 islarger than 90 degrees as shown in FIG. 13.

It is preferable that the point P1 at which these three straight linesL11, L12 and L13 are connected lies outside of a zone of the opticalspot formed by the above-mentioned reflected light 11. Also, it ispreferable that the above-mentioned angles θ1 and θ2 formed between theseparating line L11 for the areas C and D and the respective ones of theother two separating lines L12 and L13 are determined such that theother two separating lines L12 and L13 may be tangential lines to thecircle of the above-mentioned optical spot 11, as shown in FIG. 13.

By configuring the hologram 23 as described above, the optical spotformed by the reflected light 11 is completely included in the area AB,and, thus, it is possible to reduce the adverse influence caused by theflares. Furthermore, the qualities of the tracking error signalexpressed by:

TES=(c−d)−α((e+g)−(f+h)),

the tracking cross signal expressed by:

TCS=(c+d)−α((e+g)+(f+h)), and

the lens position signal expressed by:

LPS=(c−d)+α((e+g)−(f+h))

are improved.

FIG. 14 illustrates a hologram 24 provided in an optical pickupapparatus in a fifth embodiment of the present invention, which hologramalso acts as a beam splitting device.

In the fifth embodiment, instead of the hologram 4 provided in theabove-described optical pickup apparatus shown in FIG. 1, the hologram24 is formed on the glass plate 2.

The hologram 24 has total four areas, i.e., two areas C and D fordetecting the push-pull signal, an area AB for detecting the focus errorsignal and an area I including the center of the optical axis, whichfour areas are defined by four separating lines L21, L22, L23 and L24.Specifically, by the circular separating line L24 having the centercoincident with the optical axis and having the diameter larger than theoptical spot of the reflected light 11, the area I is defined from theothers. Then, the other areas C, D and AB are defined by the threestraight separating lines L21, L22 and L23.

FIGS. 15A and 15B illustrate a state of the reflected light after beingdiffracted by the hologram 24 shown in FIG. 14. By means of the grating3 shown in FIG. 2, the beam reflected by the optical disk 8 is splitinto three beams, i.e., a main beam and two sub-beams, which beams arethen split by means of the hologram 24. As a result, the reflected light10 from the recording layer 8 a forms total 12 optical spots, while thereflected light 11 from the recording layer 8 b do not focus on thelight receiving device 9 and form three flares there.

In this embodiment, the light receiving device 9 has nine lightreceiving surfaces, ‘a’ through ‘i’, as shown in FIGS. 15A and 15B.Beams created by the diffraction performed on the light with the fourareas AB, C, D and I shown in FIG. 14 of the hologram 24 and therespective light receiving surfaces to which the these beams are appliedhave the following relationship:

The diffracted light of the main beam from the area AB is receivedbetween the light receiving surfaces ‘a’ and ‘b’;

The diffracted light of the main beam from the area C is received by thelight receiving surface ‘c’;

The diffracted lights of the sub-beams from the area C are received bythe light receiving surfaces ‘e’ and ‘g’, respectively;

The diffracted light of the main beam from the area D is received by thelight receiving surface ‘d’;

The diffracted light of the sub-beams from the area D are received bythe light receiving surfaces ‘f’ and ‘h’ respectively; and

The diffracted light of the main beam from the area I is received by thelight receiving surface ‘i’.

The diffracted lights of the sub-beams from the area AB are receivedoutside of the light receiving surface ‘a’ and the light receivingsurface ‘b’, respectively; and the diffracted lights of the sub-beamsfrom the area I are received outside of the light receiving surface ‘i’,respectively. In other words, these diffracted lights are notsubstantially received by the light receiving device 9, as shown inFIGS. 15A and 15B.

By expressing the various signals obtained from the respective lightreceiving surfaces ‘a’ through ‘i’ by the same symbols ‘a’ through ‘i’respectively, the focus error signal FES is expressed by:

FES=a−b.

A tracking error signal TES is expressed by:

TES=(c−d)−α((e+g)−(f+h)).

A tracking cross signal TCS is expressed by:

TCS=(c+d)−α((e+g)+(f+h)).

A lens position signal LPS is expressed by:

LPS=(c−d)+α((e+g)−(f+h))

An information reproducing signal RFS is expressed by:

RFS=a+b+c+d+i.

Thus, as the flare of the reflected light from the recording layer 8 bis applied only to the light receiving surface ‘i’, the above-mentionedrespective ones of the various signals can be properly detected.

The present invention is not limited to these embodiments describedabove. For example, although the hologram device is applied as the beamsplitting device in each of these embodiments, another optical devicesuch as a prism, a lens or so may also be applied instead.

Recently, as a large-information-storage capacity optical disk, a DVD(digital versatile disk) has spread. DVD-RAM•WO, DVD-R, DVD+R, DVD-RAM,DVD-RW and DVD+RW are recordable disks. Thereamoung, DVD-RAM•WO, DVD-Rand DVD+R are write-once disks (writing can be made only once), whileDVD-RAM, DVD-RW and DVD+RW are rewriteable disks (writing can be made aplurality of times). Information recording/reproduction is made ontothese various types of DVDs, i.e., optical disks by means of an opticaldisk drive apparatus having a configuration as shown in FIG. 16.

FIG. 16 shows a general functional block diagram of an optical diskdrive apparatus according to one embodiment of the present invention. Asshown, this apparatus handles an optical disk 51, and includes a spindlemotor 52, an optical pickup apparatus 53, a motor driver 54, a readamplifier 55, a servo unit 56, a DVD decoder 57, an ADIP decoder 58, alaser controller 59, a DVD encoder 60, a DVD-ROM encoder 61, a bufferRAM 62, a buffer manager 63, a DVD-ROM decoder 64, a ATAPI/SCSIinterface 65, a D/A converter 66, a ROM 67, a CPU 68, and a RAM 69. Theoptical pickup apparatus applies a laser beam LB onto the optical disk51, and an audio output signal Audio is obtained from the D/A converter66 finally.

In FIG. 16, arrows denote directions in which data flows, and the CPU 67controls the respective blocks although lines denoting signal connectionbetween blocks therefor are omitted. In the ROM 67, control programswritten in a code which can be recognized by the CPU 68 is stored. Uponturning on of a power supply to the optical disk drive apparatus, theabove-mentioned control programs are loaded into a main memory (notshown), the CPU 68 controls operation of the respective parts accordingto the programs, and stores data or so necessary for the control intothe RAM 69.

Configuration and operation in the optical disk drive apparatus will nowbe described.

The optical disk 51 is rotated by the spindle motor 52. The spindlemotor 52 is controlled by the motor driver 54 and servo unit 56 so thatthe linear velocity or angular velocity is made constant. The linearvelocity or angular velocity can be controlled stepwise.

The optical pickup apparatus 53 has therein an optical system accordingto any of the first through fifth embodiments described above withreference to FIGS. 1 through 4 and 9 through 15B, and also, has a focusactuator, a tracking actuator, the light receiving device 9 (see FIG.1), and a position sensor. The optical pickup apparatus 53 applies thelaser beam LB onto the optical disk 51 as mentioned above. Further, theoptical pickup apparatus 53 can be moved in a sledge direction by aseeking motor. These focus actuator, tracking actuator and seeking motorare controlled by the motor driver 54 and servo unit 56 based on signalsobtained from the light receiving device and position sensor, so thatthe spot formed by the laser beam LB may be located at a target positionon the optical disk 51.

Then, at a time of reading operation, a reproduced signal obtained bythe optical pickup apparatus 53 is amplified by the read amplifier 55and binarized. After that, the signal is input to the DVD decoder 57.The binarized signal thus input is 8/16-demodulated by the DVD decoder57. The recorded data in the optical disk 51 is modulated ( 8/16modulation) in a manner in which 8 bits are collected as a unit, and,the above-mentioned decoding operation converts the 8 bits into 16 bits.In this case, coupling bits are added such that the respective numbersof ‘1’ and ‘0’ are made equal on average. This process is called ‘DCcomponent suppression’, and thereby, slice level fluctuation in thereproduced signal after having undergone a DC cutting process can besuppressed.

The thus-obtained demodulated data undergoes de-interleave and errorcorrection. After that, the data is input to the DVD-ROM decoder 64,and, in order to improve reliability, further error correction isperformed thereon. The data having undergone two times of errorcorrection operations are once stored in the buffer RAM 62 by the buffermanager 63. Then, after the thus-stored data becomes equal to sectordata, the data is then transferred to a host computer (not shown) viathe ATAPI/SCSI interface 65. In case of music data, data output from theDVD decoder 57 is input to the D/A converter 66, and an analog audiooutput signal Audio is obtained therefrom.

At a time of writing, data sent from the host computer via theATAPI/SCSI interface 65 is once stored in the buffer RAM 62 by thebuffer manager 63. After that, writing operation is started. In thiscase, it is necessary to previously position the laser spot at aposition on the optical disk 51 from which writing is to be started.This position is obtained from a wobble signal in a form of wobbling oftrack previously provided in the optical disk 51 in case of DVD+RW/+R.In case of DVD-RW/-R, instead of the wobble signal, a land pit is usedfor the same purpose. In case of DVD-RAM/RAM•WO, a pre-pit is used forthe same purpose.

In the wobble signal in the DVD+RW/+R disk, address information calledADIP (address in pre-groove) is included, and this information isextracted by the ADIP decoder 58. Furthermore, a synchronization signalextracted by this ADIP decoder 58 is input to the DVD encoder 60, andthereby, writing to the optical disk 51 at a proper position is ensured.The data in the buffer RAM 62 is processed by the DVD-ROM encoder 61 orthe DVD encoder 60 so that addition of error correction code orinterleave is performed, and then is written to the optical disk 51through the laser controller 59 and optical pickup apparatus 53. Theaddress information may be obtained from the land pit or pre-pitinstead.

FIG. 17 shows a block diagram of an information processing apparatusemploying the above-mentioned optical disk drive apparatus shown in FIG.16. As shown, this apparatus includes a main control device 70, aninterface 71, a recording device 72, an input device 73, a displaydevice 74, the optical disk drive apparatus 75 shown in FIG. 16, and soforth. The main control device includes a CPU, a microcomputer, a mainmemory and so forth, and controls the entirety of the informationprocessing apparatus.

The interface 71 provides a bidirectional communication interfacebetween the optical disk drive apparatus 75 and the main control device70, and conforms to standard interfaces of ATAPI, SCSI and so forth. Theinterface 71 is connected with the interface 65 in the optical diskdrive apparatus shown in FIG. 16. A connection manner between therespective interfaces is not only cable connection employing acommunication cable (for example, a SCSI cable) but also wirelessconnection employing infrared ray or so.

In the recording device 72 such as a hard disk drive (HDD), programswritten in a code recognizable by the microcomputer of the main controldevice 70 are stored. Upon turning on of a power supply to theinformation processing apparatus, the above-mentioned programs areloaded into the main memory of the main control device 70.

The display device 74 includes a CRT, a liquid crystal device, a plasmadisplay device or so, and displays various types of information from themain control device 70. The input device 73 includes a keyboard, amouse, a pointing device or so, and provides information input by theuser to the main control device 70. Information from the input device 73may be provided by air to the main control device 70. For example, a CRTwith a touch panel or so which includes both the display device 70 andinput device 73 in a unit may be applied.

The information processing apparatus has an operation system (OS)mounted therein, and all the devices/components included in theinformation processing apparatus are managed by the OS.

Thus, according to the present invention in an aspect concerning theabove-mentioned first through fifth embodiments, it is possible toreduce the adverse influence exerted onto the focus error signal (FES),tracking error signal (TES), tracking cross signal (TCS), lens positionsignal (LPS), information reproducing signal (RFS) caused due toreflected light from the recording layer of the optical disk fartherfrom the objective lens when focus occurs in the recording layer of theoptical disk nearer to the objective lens.

Sixth through ninth embodiments of the present invention will now bedescribed with reference to figures. Each of these embodiments has aconfiguration same as that of the related art described above withreference to FIGS. 5 through 8 except the following configuration. Thesame reference numerals are given to the same devices/components in theconfiguration described above with reference to FIGS. 5 through 8.

FIG. 18 illustrates a configuration of the above-mentioned hologram 104and a position of the reflected light therein according to the sixthembodiment.

According to the sixth embodiment, with respect to the hologram 104 inthe optical pickup apparatus shown in FIG. 5, the position of theoptical axis of the reflected light from the optical disk 108 applied tothe hologram 104 is largely shifted to the side of the above-mentionedtwo areas C and D for detecting the push-pull signal as shown in FIG. 18(also see FIG. 7 in a comparing manner).

The push-pull signal is obtained from the hatched zones in FIG. 7 asmentioned above of the spot of the reflected light 110. In the case ofFIG. 7 described above, the point at which the separating lines for theareas AB, C and D are connected coincides with the center of the opticalaxis of the reflected light 110, and in that case, approximately 50% ofthese hatched zones in the area rate is included in the areas C and D asshown in FIG. 7.

In contrast thereto, according to the sixth embodiment of the presentinvention, as shown in FIG. 18, the configuration is made such that theoptical axis of the reflected light 110 applied is largely shiftedtoward the areas C and D with respect to the above-mentioned point P51at which the separating lines L51, L52 and L53 are connected. As aresult, more than 50% of the zones Z1 and Z2 of the reflected light 110from which the push-pull signal is obtained is made to be included inthe areas C and D for detecting the push-pull signal as shown in FIG.18.

By providing the above-mentioned configuration, it is possible to obtaina large amount of light for detecting the push-pull signal. Inparticular, as more than 50% of the light amount of the push-pull signalof the reflected light 110 from the optical disk 108 is made to beapplied within the areas C and D as mentioned above, it is possible toproperly detect information therefrom such as addresses or so written inthe pre-groove of the DVD+RW/+R mentioned above.

As the configuration is provided such that the reflected light 110 ismade to be applied to the hologram 104 as shown in FIG. 18, the lightamount received by the area AB is reduced. As a result, there may occura problem in which operation of a circuit for detecting signals with ause of the light receiving signals obtained from the areas AB, C and Dcannot be performed properly. For example, a problem may occur in which,as the light amount received by the areas C and D are increased asmentioned above, a circuit generating the push-pull signal is saturated,or, as the light amount received by the area AB may become too small togenerate the focus error signal properly. The seventh embodiment of thepresent invention is devised so as to solve this problem.

FIG. 19 shows a configuration of a hologram provided in an opticalpickup apparatus according to the seventh embodiment of the presentinvention as well as a position of the reflected light 110 appliedthereto. According to the seventh embodiment, instead of the hologram104 shown in FIG. 18, a hologram 121 is formed on the glass plate 102.

In the hologram 121 shown in FIG. 19, in a central portion, portions ofthe separating line L52 and L53 between the area AB and areas C and D(in FIG. 18) around the point P51 at which the separating lines L51, L52and L53 are connected are curved toward the side of the areas C and Dbut in a manner in which the area AB may not overlaps the hatched zonesZ1 and Z2 for generating the push-pull signal as shown in FIG. 19. Inother words, the separating lines L51, L52 and L53 in FIG. 18 definingthe areas AB, C and D are formed with three straight lines L61, L62 andL64, and a curved line L63 as shown in FIG. 19.

By configuring the hologram in the seventh embodiment as describedabove, it is possible to increase the light amount received by the areaAB in comparison to the sixth embodiment shown in FIG. 18. Accordingly,it is possible to make approximately equal the light amounts received bythe areas A and the areas C and D, and also, while still increasing onlythe light amount for generating the push-pull signal. In fact, as shownin FIG. 19, a large area of the zones Z1 and Z2 is still included in theareas C and D as in the case of FIG. 18, and thus, the light amount forgenerating the push-pull signal can be sufficiently provided thereby. Asa result, it is possible to eliminate the possibility of theabove-mentioned problem in which the light amount is too small togenerate the focus error signal properly while securing the light amountfor generating the push-pull signal.

FIG. 20 shows a configuration of a hologram provided in an opticalpickup apparatus according to the eight embodiment of the presentinvention, and a position of the reflected light applied thereto.According to the eighth embodiment, instead of the hologram 104 shown inFIG. 18, a hologram 122 is formed on the glass plate 102 shown in FIG.20.

This hologram 122 is such that straight lines L62 and L64 which dividesthe hologram into the area AB and areas C and D in the hologram 121described above with reference to FIG. 19 are rotated in respectivedirections indicated by arrows A71 and A72 shown in FIG. 20 about thepoints P71 and P72 at which the curved line L63 and the straight linesL62 and L64 are connected shown in FIG. 19, respectively. As a result,the separating lines L72 and L74 shown in FIG. 20 are provided.

By configuring the hologram 122 as described above, it is possible tofurther increase the area receiving the light amount for detecting thepush-pull signal in comparison to the hologram 121 shown in FIG. 19.

In this configuration, by setting the above-mentioned straight lines L72and L74 rotated as mentioned above so that these lines L72 and L74 maybe tangential lines to the hatched zones Z1 and Z2, or these lines L72and L74 pass through points P and Q which are the respective ends of thezones Z1 and Z2 on the side of the area AB, it is possible that thehatched zones Z1 and Z2 are completely included in the areas C and D,thus, the push-pull signal can be satisfactory detected, while the lightamount received by the area AB can be secured too.

FIG. 21 shows a configuration of a hologram 123 provided in an opticalpickup apparatus according to the ninth embodiment of the presentinvention as well as a position of the reflected light applied thereto.According to the ninth embodiment, instead of the hologram 104 to whichthe reflected light 110 is applied as shown in FIG. 18, the hologram 123is formed on the glass plate 102 shown in FIG. 21.

In the hologram 123, a point P81 at which the areas AB, C and D areconnected together is shifted toward the side of the areas C and D withrespect to the optical axis of the reflected light 110 applied, theareas AB, C and D are defined by three straight lines L81, L82 and L83acting as separating lines extending from the above-mentioned connectingpoint P81 in a manner such that the area rate of parts of the hatchedzones Z1 and Z2 included in the areas C and D with respect to the entirearea of the zones Z1 and Z2 may be more than 50%. Furthermore, each ofthe separating lines L82 and L83 forms an angle θ1/θ2 lager than 90degrees with respect to the separating line L81 for the areas C and D,as shown in FIG. 21.

By configuring as described above, it is possible to increase the areareceiving the light amount for detecting the push-pull signal incomparison to the hologram 104 shown in FIG. 18. In the ninthembodiment, although the separating lines L81, L82 and L83 only includestraight lines, same advantage as that in the case of FIG. 20 can beexpected.

In this configuration, by setting the two separating lines L82 and L83to form the angles θ1 and θ2 such that these lines L82 and L83 aretangential lines to the hatched zones Z1 and Z2, respectively, thehatched zones Z1 and Z2 are included by the areas C and D so that thepush-pull signal can be satisfactorily detected therefrom, and also, thelight amount received by the area AB can be secured too.

The present invention is not limited to these embodiments describedabove. For example, although the hologram device is applied as the beamsplitting device in each of these embodiments, another optical devicesuch as a prism, a lens or so may be applied instead. Especially, in theconfiguration shown in FIG. 21, the separating lines include onlystraight lines as mentioned above, and thus, this configuration can beeasily achieved by prisms, for example.

Recently, as a large-information-storage capacity optical disk, a DVD(digital versatile disk) has spread. DVD-RAM•WO, DVD-R, DVD+R, DVD-RAM,DVD-RW, DVD+RW are recordable disks. Thereamoung, DVD-RAM•WO, DVD-R andDVD+R are write-once disks (writing can be made only once), whileDVD-RAM, DVD-RW and DVD+RW are rewriteable disks (writing can be made aplurality of times). Information recording/reproduction is made ontothese various types of DVDs, i.e., optical disks by means of an opticaldisk drive apparatus having a configuration as shown in FIG. 22.

FIG. 22 shows a general functional block diagram of an optical diskdrive apparatus according to another embodiment of the presentinvention. As shown, this apparatus handles an optical disk 151, andincludes a spindle motor 152, an optical pickup apparatus 153, a motordriver 154, a read amplifier 155, a servo unit 156, a DVD decoder 157,an ADIP decoder 158, a laser controller 159, a DVD encoder 160, aDVD-ROM encoder 161, a buffer RAM 162, a buffer manager 163, a DVD-ROMdecoder 164, a ATAPI/SCSI interface 165, a D/A converter 166, a ROM 167,a CPU 168 and a RAM 169. The optical pickup apparatus applies a laserbeam LB onto the optical disk 151, and an audio output signal Audio isobtained from the D/A converter 166 finally.

In FIG. 22, arrows denote directions in which data/signal flows, and theCPU 167 controls the respective blocks although lines denoting signalconnection between blocks therefor are omitted. In the ROM 167, controlprograms written in a code which can be recognized by the CPU 168 arestored. Upon turning on of a power supply to the optical disk driveapparatus, the above-mentioned control programs are loaded into a mainmemory (not shown), the CPU 168 controls operation of the respectiveparts according to the programs, and temporarily stores data or sonecessary for the control into the RAM 169.

Configuration and operation in the optical disk drive apparatus will nowbe described.

The optical disk 151 is rotated by the spindle motor 152. The spindlemotor 152 is controlled by the motor driver 154 and servo unit 156 sothat the linear velocity or angular velocity is made constant. Thelinear velocity or angular velocity can be controlled stepwise.

The optical pickup apparatus 153 has therein an optical system in any ofthe sixth through ninth embodiments described above with reference toFIGS. 5 through 8 and 18 through 21, and also, has a focus actuator, atracking actuator, the light receiving device 109 (see FIG. 5), and aposition sensor. The optical pickup apparatus 153 applies the laser beamLB onto the optical disk 151 as mentioned above. Further, the opticalpickup apparatus 153 can be moved in a sledge direction by a seekingmotor. These focus actuator, tracking actuator and seeking motor arecontrolled by the motor driver 154 and servo unit 156 based on signalsobtained from the light receiving device and position sensor, so thatthe spot formed by the laser beam LB is located at a target position onthe optical disk 151.

Then, at a time of reading operation, a reproduced signal obtained bythe optical pickup apparatus 153 from the optical disk is amplified bythe read amplifier 155 and binarized. After that, the signal is input tothe DVD decoder 157. The binarized signal thus input is 8/16-demodulatedby the DVD decoder 157. The recorded data in the optical disk 151 ismodulated ( 8/16 modulation) in a manner in which 8 bits are collectedas a unit, and, the above-mentioned decoding operation converts 8 bitsinto 16 bits. In this case, coupling bits are added such that thenumbers of ‘1’ and ‘0’ are made equal on average. This process is called‘DC component suppression’, and thereby, slice level fluctuation of thereproduced signal after having undergone a DC cutting process issuppressed.

The thus-obtained demodulated data undergoes de-interleave and errorcorrection. After that, the data is input to the DVD-ROM decoder 164,and, in order to improve reliability, further error correction isperformed thereon. The data having undergone two times of errorcorrection operations are once stored in the buffer RAM 162 by thebuffer manager 163. Then, after the thus-stored data become equal tosector data, the data is transferred to a host computer (not shown) viathe ATAPI/SCSI interface 165. In case of music data, data output fromthe DVD decoder 157 is input to the D/A converter 166, and an analogaudio output signal Audio is obtained therefrom.

At a time of writing, data sent from the host computer via theATAPI/SCSI interface 165 is once stored in the buffer RAM 162 by thebuffer manager 163. After that, writing operation is started. In thiscase, it is necessary to previously position the laser spot at aposition on the optical disk from which writing is to be started. Thisposition is obtained from a wobble signal in a form of wobbling of atrack previously provided in the optical disk 151 in case of DVD+RW/+R.In case of DVD-RW/-R, instead of the wobble signal, a land pit is usedfor the same purpose. In case of DVD-RAM/RAM•WO, a pre-pit is used forthe same purpose.

In the wobble signal in the DVD+RW/+R disk, address information calledADIP (address in pre-groove) is included, and this information isextracted by the ADIP decoder 158. Furthermore, a synchronization signalextracted by this ADIP decoder 158 is input to the DVD encoder 160, andthereby, writing to the optical disk 151 at a proper position issecured. The data in the buffer RAM 162 is processed by the DVD-ROMencoder 161 or the DVD encoder 160 so that addition of error correctioncode or interleave is performed, and then is written to the optical disk151 through the laser controller 159 and optical pickup apparatus 153.The address information may be obtained from the land pit or pre-pitinstead.

FIG. 23 shows a block diagram of an information processing apparatusemploying the above-mentioned optical disk drive apparatus shown in FIG.22. As shown, this apparatus includes a main control device 170, aninterface 171, a recording device 172, an input device 173, a displaydevice 174, the optical disk drive apparatus 175 shown in FIG. 22 and soforth. The main control device includes a CPU, a microcomputer, a mainmemory and so forth, and controls the entirety of the informationprocessing apparatus.

The interface 171 provides a bidirectional communication interfacebetween the optical disk drive apparatus 175 and the main control device170, and conforms to standard interfaces of ATAPI, SCSI and so forth.The interface 171 is connected with the interface 165 in the opticaldisk drive apparatus shown in FIG. 22. A connection manner between therespective interfaces is not only cable connection employing acommunication cable (for example, SCSI cable) but also wirelessconnection employing infrared ray or so.

In recording device 172 such as a hard disk drive (HDD), programswritten in a code recognizable by the microcomputer of the main controldevice 170 are stored. Upon turning on of a power supply to theinformation processing apparatus, the above-mentioned programs areloaded into the main memory of the main control device 170.

The display device 174 includes a CRT, a liquid crystal device, a plasmadisplay device or so, and displays various types of information from themain control device 170.

The input device 173 includes a keyboard, a mouse, a pointing device orso, and provides information input by the user to the main controldevice 170. Information from the input device 173 may be provided by airto the main control device. For example, a CRT with a touch panel or sowhich includes both the display device 170 and input device 173 in aunit may be applied.

The information processing apparatus has an operation system (OS)mounted therein, and all the devices/components included in theinformation processing apparatus are managed buy the OS.

Thus, according to the present invention in an aspect concerning theabove-described sixth through ninth embodiments, it is possible tosecure the light amount required for detecting the push-pull signal,and, thereby, it is possible to properly detect information such asaddresses written in the pre-groove of a DVD+RW/+R, for example.

Further, the present invention is not limited to the above-describedembodiments, and variations and modifications may be made withoutdeparting from the basic concept of the present invention.

The present application is based on Japanese priority applications Nos.2003-020440, 2003-032198, 2003-032204 and 2003-040898, filed on Jan. 29,2003, Feb. 10, 2003, Feb. 10, 2003 and Feb. 19, 2003, the entirecontents of which are hereby incorporated by reference.

1.-14. (canceled)
 15. An optical pickup apparatus for applying throughan objective lens a beam from a semiconductor laser to an optical diskhaving two recording layers, introducing reflected light from theoptical disk to a focus-error-signal-detecting light receiving deviceand a track-error-signal-detecting light receiving device through theobjective lens and a beam splitting part, and reproducing informationfrom the optical disk, wherein: when the beam from the semiconductorlaser is focused on one of the two recording layers through theobjective lens, the beam splitting part splits the beam in such a manneras to apply the reflected light from the recording layer of the tworecording layers, on which the beam is focused, to thefocus-error-signal-detecting light receiving device and thetrack-error-signal-detecting light receiving device, and also, toprevent the reflected light from the recording layer of the tworecording layers, on which the beam is not focused, from being appliedto at least one of the focus-error-signal-detecting light receivingdevice and the track-error-signal-detecting light receiving device. 16.The optical pickup apparatus as claimed in claim 15, wherein: therecording layer of the two recording layers, on which the beam isfocused, is the recording layer which is nearer to the objective lens.17. The optical pickup apparatus as claimed in claim 15, wherein: thelight splitting part has its area separated by a separating line whichis larger than a diameter of an area to which the reflected light fromthe recording layer of the two recording layers on which the beam is notfocused is applied to the light beam splitting part.
 18. The opticalpickup apparatus as claimed in claim 15, wherein: the beam splittingpart comprises a hologram device.
 19. An optical disk drive comprisingthe optical pickup apparatus as claimed in any one of claims 15-18.